This invention relates to a curable composition and especially to those that can have controlled cure through the use of appropriate curing agents. In its most preferred and presently useful form the invention provides relief printing plates which are characterized by unusually good dimensional stability coupled with improved solvent resistance and non-tacky surfaces while retaining the many desirable properties espoused for other plates and often with enhanced quality.
The preferred relief layer composition is preferably provided with a preferred under-lamina that will stabilize the finished printing plate against creep, physical deformation and stress relaxation in the polymer structure.
The preferred over-lamina gives excellent use with a wide variety of ink formulations. Fortunately the expansion, contraction and other distortion properties of the over-lamina and the under-lamina are compatible for long press runs without failures. This is particularly true with the preferred compositions and layered constructions.
Many patents independently reveal various features of the inventive structure and its preferred inventive embodiments. They however lack the overall advantage presented by the synergistic effectiveness of the present new compositions, methods and structures. U.S. Pat. No. 3,024,180 discloses a photopolymerizable composition having at least 40% by weight of solvent-soluble elastomeric homopolymer of poly (chloro-2-butadiene-1,3) and at least 10% by weight of addition polymerizable ethylenically unsaturated compound containing 1 to 2 terminal ethylenic groups plus an initiator. U.S. Pat. No. 3,674,486 and British Pat. No. 1,366,769 disclose compositions having an A-B-A type block copolymer. Similar A-B block copolymer compositions are disclosed in German Patent Publications DT OS Nos. 24 56 439 and DT OS 26 10 206. French Patent Publication No. 2,103,825 reveals acrylonitrile-butadiene copolymer compositions also containing an acrylate monomer.
There are a number of U.S. and foreign patents that show photocurable compositions that have as a major chemically functioning constituent a polythiol. This is unlike the present invention where the polythiol constituent seemingly acts in some way to regulate and make more effective the polymerization of the constituent components of the composition. Examples of patents that show photocurable compositions that have a polythiol as a major chemically functioning constituent are U.S. Pat. Nos. 4,008,341; 3,843,572; 3,832,421; 3,783,152; 3,666,461; 3,661,744; 3,627,529 and 3,615,450 and Canadian Pat. Nos. 930,094; 926,183; 924,047 and 885,388.